1. Field of the invention
The present invention relates to a continuous vacuum lamination treatment system and a vacuum lamination apparatus. More particularly, the present invention relates to a continuous vacuum lamination treatment system which enables mass-production of a solar cell module at a high throughput and a vacuum lamination apparatus suitable for producing a solar cell module.
2. Related Background Art
There are known various vacuum lamination apparatus used at a final stage in the production of semiconductor devices such as solar cells and the like which are used while exposed to outside air, in order to seal such semiconductor device such that it is sufficiently durable against changes in the environmental temperature and humidity and also against impact or destructive force applied thereto. Solar cell modules produced through these vacuum lamination apparatus are used as a power generation source of providing clean energy without causing pollution.
In recent years, earth environmental pollution has been spreading worldwide, and along with this, the public consciousness for earth environmental protection has been increasing on a worldwide scale. Particularly, serious apprehension has arisen regarding heating the earth because of the so-called greenhouse effect due to an increase of atmospheric CO.sub.2. In this connection, there is an increased social demand for early realization of a power generation system capable of providing clean energy without causing CO.sub.2 buildup as in the case of thermal power generation.
Under this situation, public attention has focused on the power generation system using a solar cell since the solar cell has advantages such that it is safe, can be readily handled and that it can be used as a power generation source of providing clean energy without causing CO.sub.2 buildup. And various studies have been made in order to produce a highly reliable solar cell with a reasonable production cost. In the production of such solar cell, the foregoing vacuum lamination apparatus pays an important role.
Incidentally, there have been proposed a variety of solar cells which are different in terms of the type and configuration. Representative specific examples of these solar cells are single crystal silicon solar cells, polycrystal silicon solar cells, amorphous silicon solar cells, copper indium selenide solar cells, and compound semiconductor solar cells. Of these solar cells, various research and development studies have been made on so-called thin film crystal silicon solar cells, compound semiconductor solar cells and amorphous silicon solar cells since they can be relatively easily produced to have a large area at a relatively low production cost.
In order to practically use these solar cells as a power generation source, for instance, in outdoors, they are designed into a solar cell module having a desired configuration which can be used as a power generation source.
FIGS. 13(a) and 13(b) are schematic views illustrating an example of the configuration of such a solar cell module. Particularly, FIG. 13(a) is a schematic cross-sectional view illustrating an example of the constitution of a laminate comprising given constituent members for a solar cell module and which is to be subjected to thermocompression treatment in order to produce a solar cell module. FIG. 13(b) is a schematic cross-sectional view illustrating a stacked body as a solar cell module obtained as a result of having subjected the laminate shown in FIG. 13(a) to thermocompression treatment. In FIGS. 13(a) and 13(b), reference numeral 1001 indicates a surface side covering member, reference 1002 a filler, reference numeral 1003 a solar cell (or a photovoltaic element), and reference numeral 1004 a back side covering member.
The above solar cell module is prepared, for instance, as will be described in the following. First, the foregoing constituent members for a solar cell are laminated to obtain such a laminate as shown in FIG. 13(a). The laminate thus obtain is introduced into a vacuum lamination apparatus, where the laminate is positioned therein while being hermetically enclosed, followed by vacuuming the inside of the laminate to release air present in the laminate to the outside. Then, while continuing the vacuuming operation, the laminate is subjected to heat treatment, where the laminate is heated to a predetermined temperature at which the fillers are crosslinked or cured. This heat treatment is continued at this temperature for a prescribed period of time until the fillers are sufficiently cured, followed by cooling the laminate thus treated. After this, the vacuuming operation is terminated to return the atmosphere surrounding the laminate to atmospheric pressure, followed by taking out the laminate. By this, a solar cell module having the configuration shown in FIG. 13(b) is obtained.
FIGS. 14(a) through 14(c) are schematic diagrams illustrating a conventional vacuum lamination apparatus which is used for the production of a solar cell module. Particularly, FIG. 14(a) is a schematic diagram illustrating the entire vacuum lamination apparatus, FIG. 14(b) is a schematic cross-sectional view, taken along the F--F line in FIG. 14(a), and FIG. 14(c) is a schematic cross-sectional view illustrating a structural embodiment provided upon producing a solar cell module.
In FIGS. 14(a) through 14(c), reference numeral 1101 indicates a mounting table having a mounting area A on which a stacked body (or a laminate) 1108 for a solar cell module is to be positioned. Reference numeral 1102 indicates a vacuuming tube which is provided with a plurality of vents 1105 and which is arranged so as to circumscribe the mounting area A of the mounting table 1101. Reference numeral 1103 indicates a valve provided at an exhaust pipe 1110 which is communicated with the vacuuming tube 1102 at one end thereof and which is connected to a vacuuming pump 1104 at the other end thereof. Reference numeral 1106 indicates a fixing means to fix the vacuuming tube 1105 to the mounting table 1101. Reference numeral 1107 indicates a flexible covering member, and reference numeral 1109 a netted member.
The preparation of a solar cell module using the vacuum lamination apparatus shown in FIG. 14(a) through FIG. 14(c) is conducted, for instance, in the following manner. The netted member 1109 is laid on the surface of the mounting area A of the mounting table 1101. A stacked body (or a laminate) for producing a solar cell module as the stacked body 1108 (see, FIG. 14(c)) is positioned on the netted member 1109 laid on the mounting area A. The flexible covering member is superposed over the stacked body 1108 on the mounting table 1101 while hermetically sealing between the mounting table and the flexible covering member. The vacuuming pump 1104 is actuated to exhaust the inside of the space containing the stacked body 1108 between the flexible covering member 1107 and the mounting area A circumscribed by the vacuuming tube 1105 through the vents 1105 of the vacuuming tube, whereby the flexible covering member 1107 is sagged toward the mounting table side to compress the stacked body 1108. While operating the vacuuming pump 1104, the lamination apparatus is introduced into an oven (not shown) maintained at a predetermined temperature, where the stacked body is subjected to heat treatment at a temperature at which the fillers contained in the stacked body are cured. This heat treatment is continued until the fillers of the stacked body are sufficiently cured. After this, while continuing the operation of the vacuuming pump, the lamination apparatus is taken out from the oven, followed by cooling the stacked body. Then, the operation of the vacuuming pump is terminated to return the inside atmosphere of the foregoing space to atmospheric pressure. By this, the preparation of a solar cell module is completed.
This conventional vacuum lamination apparatus has advantages such that the scale of the apparatus can be readily adjusted depending upon the size of a solar cell module to be prepared since the structure thereof is relatively simple, specifically, for instance in the case of preparing a solar cell module having a large area, it can be readily enlarged; since the calorific capacity of the apparatus is small, the constituent materials of a stacked body for a solar cell module can be heated to a desired temperature within a short period of time; and the period of time required for the preparation of a solar cell module can be shortened.
Although the conventional vacuum lamination apparatus has such advantages as above described, it has such shortcomings as will be described in the following, for example, in a case of mass-producing a large area solar cell module and therefore, it is not suitable in the case of mass-producing such large area solar cell module.
In order for the production system to mass-produce a large area solar cell module, it is required to have a large-sized heating oven capable of accommodating a large-sized vacuum lamination instrument (or a large-sized vacuum lamination apparatus) therein, which is the largest in terms of the plant and equipment investment.
Particularly in this respect, the vacuum lamination treatment in the production of a solar cell module comprises (1) laminating constituent members for the production of a solar cell module, (2) vacuuming a stacked body obtained in the step (1), (3) heating the vacuumed stacked body, (4) cooling the heat-treated stacked body, and (5) taking out the stacked body cooled in the step (4). The heating oven is used in only one of these five steps, i.e., the heat treatment step (3). In order for the heating oven to be most efficiently utilized in the production system to mass-produce a solar cell module, it is necessary that a plurality of vacuum lamination instruments (or vacuum lamination apparatus) are provided, each lamination instrument is designed such that it can quickly and efficiently travel each of the foregoing steps, and the entire of the system is optimized. In the case where the solar cell module to be mass-produced is of a large area, each lamination instrument is required to have a large size suited for the solar cell module. The large-sized lamination instrument is heavy and difficult to handle.
By the way, in the foregoing vacuum lamination apparatus shown in FIGS. 14(a) through 14(c), the fixing means 1106 is used for fixing the vacuuming tube 1102 to the mounting table 1101 so that no clearance occurs between the vacuuming tube and the mounting table. The vacuum lamination apparatus is exposed to an atmosphere with a high temperature while the inside thereof being vacuumed in the production of a solar cell module. Therefore, the fixing means 1106 is required to be sufficiently heat-resistant. In the prior art, the vacuuming tub is fixed to the mounting table by way of welding or by means of a sealant such as RTV (room temperature vulcanization) curing type silicone sealant by which the clearance between the vacuuming tube and the mounting table is filled to fix the former to the latter. In these fixing manners, as long as the size of the mounting table and that of the vacuuming tube are small, specifically, their long sides are less than 1 m, no problem entails.
However, in recent years, there is an increased demand for a production system capable of efficiently mass-producing a large area solar cell with a reasonable production cost, wherein the mounting table and the vacuuming pipe of the vacuum lamination apparatus used are required to be large-sized.
The foregoing conventional vacuum lamination apparatus does not sufficiently satisfy this demand. That is, in the case where the mounting table and the vacuuming tube are large-sized, when the large-sized vacuuming tube is fixed to the large-sized mounting table by any of the foregoing fixing manners, such problems exist, as will be described below.
When the fixing manner by way of welding is employed, due to heat distortion upon the welding, the resulting vacuum lamination apparatus becomes such that is distorted.
When the fixing manner by means of the sealant, though such problem occurred in the case of the fixing manner by way of welding, there is a tendency of entailing such problems as will be described in the following. Ordinarily, the mounting table of the vacuum lamination apparatus is transported to a given step in the lamination treatment process by loading it on a specialized tool or container, and therefore, there is no problem. However, in the case of taking the mounting table away from the specialized tool or container for the purpose of apparatus maintenance, a problem is liable to entail in that the mounting table is deformed at a certain extent because the mounting table is large in size. In this case, another problem is liable to entail in that the fixing means comprising the sealant, which is more soft than the welded fixing means, is sometimes cracked. When the fixing means is cracked, a problem occurs in that the space in the vacuum lamination apparatus cannot be vacuumed as desired and as a result, the lamination treatment for a stacked body for the production of a solar cell module cannot be conducted as desired.